There's trouble in Vancouver, the shooting location of Fox's baby-faced police series, 21 Jump Street, and its name is Richard Grieco, the show's sudden sensation, its latest titillator of teenyboppers. Sexy, dark and dangerous, the earringed actor has become any teenage girl's dream by playing her father's worst nightmare. He's TV's latest screamboat.

Picked from among 500 casting-call hopefuls to play Jump's cool-rebel newcomer, Dennis Booker, Grieco, 24, has been greeted this season by surging ratings and fan mail that avalanches in at the reported rate of 10,000 letters a month. "Girls see him and scream at the top of their lungs," says co-star Peter DeLuise. "Sometimes they achieve a pitch that's quite painful." In fact. Grieco is already such a draw that he will be spun off into a Fox series of his own next fall. Aware that his overnight stardom has caused hard feelings on the set, Grieco is unapologetic. "There are people in Jump Street who are jealous from the attention I get," he says. "The actors don't say anything, but I can tell."

In his cramped, clothing-draped hotel room, a beer in one hand and a cigarette in the other, Grieco reveals the secret of his success. "I like to add the Brando pause when I deliver my lines," he says. "I've been told every word I say 'drools with sexualit.' "Such observations, made usually by adolescent girls, are a matter of documented fact. Grabbing a handy fan letter, Grieco reads," 'Listen here, Babycakes, I love everything about you. I'd love to kiss your lips, chest, stomach.... I have juices so hot I can barely breathe.' " Adds Grieco: "I pay my mom $1,200 a month to answer these. [Brando pause.] I don't know how she does it."

Pubescent hearts may crack at the news, but Grieco's steady girlfriend for the past year has been Kimber Sissons, 28, an actress and model who played one of Spuds MacKenzie's human party-pets. After meeting at an L.A. restaurant, Grieco swept her off to Palm Springs for their first date. "It was like I was 14 again," recalls Sissons. Grieco was struck by her depth of understanding. "She helped me talk about my feelings," he says. They now share her condo in the Hollywood Hills.

It's been a wicked ride for a small-town guy from Watertown, N.Y., the eldest child of Richard Grieco Sr., a union organizer, and his wife, Carolyn, a real estate broker turned fan-mail answerer. Growing up, little Richard dreamed of playing hockey and football, not acting. But after graduating Central Connecticut State University, his linebacker fantasies had been sacked by four knee operations, so he decided to try life as a professional fantasy object. "I used to go into the cafeteria and sit alone," he says. "Suddenly there would be 20 girls around me. I started thinking, 'Man, I could do something with this charisma.' " And so he has, landing roles on One Life to Live, Who's the Boss? and The Facts of Life.

Not that he has let it go to his head. "The other day," says Grieco, "I looked in a mirror and tried to see myself objectively, as how other people saw me." The result? He pulls out a notebook and reads a poem, one of 300 he says he has written on various topics: "If you look closely, you will find a man who knows exactly what he wants, who is blessed with natural control which does not need to be harnessed but remains untamed.... Nothing is as beautiful as unleased [sic], uncontrolled energy naturally channeled into multiple facets of self-expression."

Well, Brando may be looking over his shoulder, but Shakespeare can rest easy.

—Ned Geeslin, Vicki Sheff in Vancouver